This disclosure relates to a neutron detector that distinguishes between epithermal and thermal neutrons or positions of incoming epithermal or thermal neutrons.
This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present techniques, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as an admission of any kind.
To locate and extract resources from a well, a wellbore may be drilled into a geological formation. Downhole tools are placed into the wellbore to identify properties of the downhole environment. A downhole formation density tool, for example, may be deployed within the sub-surface to measure physical properties of a surrounding geological formation. The formation density tool may include a neutron source to emit neutrons into the geological formation. Some of the neutrons may interact with the geological formation and may then be detected by a neutron detector on the formation density tool. The physical properties of the geological formation and other materials of the downhole environment may be determined from the characteristics of the detected neutrons.
Different downhole tools may include various detectors to take different measurements of the geological formation. For example, a detector for thermal neutrons may include a Helium-3 tube having Helium-3 gas that reacts with thermal neutrons to cause electrons to be detected on an anode and cathode. When measuring epithermal neutrons, the Helium-3 tube may be wrapped in a layer of shielding that stops thermal neutrons from reaching the detector. That is, the detector may detect either thermal neutrons or epithermal neutrons, but not both. To take measurements of both would involve using multiple detectors or additional time wrapping/unwrapping a detector, thereby increasing costs or decreasing efficiency of downhole operations.